Winches are well known. A conventional winch includes a drum; a crank arm configured to, when turned, rotate the drum; and a rope, cable, chain, wire, or strap having one end attached to the drum. In operation, when a user turns the crank arm in one direction, the winch winds the rope onto the drum, and when the user turns the crank arm in the opposite direction, the winch winds the rope off of the drum.
Winches are typically used (occasionally in conjunction with pulley systems) to lift objects, to lower objects, and/or to pull objects. A winch has an initial mechanical advantage that determines how difficult it is to initially turn the crank arm to lift (or lower or pull) the object and how many turns of the crank arm it takes to lift (or lower) the object to a desired height (or to pull the object a desired distance). The initial mechanical advantage of the winch is based in part on: (a) an outer diameter of the drum of the winch (and the outer circumference of the drum of the winch, which is calculated using the outer diameter); (b) the size and quantity of any gears employed in the winch; and (c) the length of the crank arm. The winch provides the initial mechanical advantage when the rope is wound completely off of the drum, and the mechanical advantage decreases as the rope is wound onto the drum and onto itself (which creates a larger effective outer diameter of the drum).
Thus, the outer diameter of the drum of the winch in part determines the initial mechanical advantage the winch provides when initially lifting (or lowering or pulling) an object. That is, the outer diameter of the drum of the winch in part determines how difficult it is to initially turn the crank arm to lift (or lower or pull) the object and how many turns of the crank arm it takes to lift (or lower) the object to a desired height (or to pull the object the desired distance). A winch providing a low initial mechanical advantage makes it more difficult to initially turn the crank arm to lift (or lower or pull) the object, but lifts (or lowers) the object to the desired height (or pulls the object the desired distance) after a relatively small number of turns of the crank arm. Conversely, a winch providing a high initial mechanical advantage makes it easier to initially turn the crank arm to lift (or lower or pull) the object, but lifts (or lowers) the object to the desired height (or pulls the object the desired distance) after a relatively large number of turns of the crank arm.
Conventional winches have drums having fixed or non-variable outer diameters and, therefore, such conventional winches have fixed or non-variable initial mechanical advantages. This can be frustrating for certain users. For instance, for a given winch, one user may prefer a higher initial mechanical advantage than the winch currently provides because the user desires to lift the object to the desired height in as few turns of the crank arm as possible. On the other hand, another user may prefer a lower initial mechanical advantage than the winch currently provides because the user finds it too difficult to turn the crank arm. Thus, there is a need for a new and improved winch having an adjustable or variable mechanical advantage that solves these problems.